Crate Blue Voodoo 6212 HELP NEEDED!!!

[GrumpyJoe]

I have a BV 6212 that is driving me crazy. It has very low volume and major distortion even on the clean channel. I pulled the circuit board out and found several cooked parts. D9,D11, D12, D13, D14, Q16, FC1, R103, R104, and R95. each of these were either visibly burnt or tested bad with my Fluke. I replaced all of the above with correct values, and i'm still having the low volume and nasty distortion. I have tried new tubes. Both EL34 and 6L6 and still no change. I do however have a bit more volume than when I started. I have also checked the pcb for the output tubes. all sockets are clean and tight, and the pins that connect J22 and J23 are clean and making good contact. I am completely lost. can someone help? I have attached the schematic for the amp. thanks

Blue Voodoo 6212 schem.pdfblue voodoo 6212 schem page 2.pdf

[Jazz P Bass]

Help us out here.

Where are these parts and on which schematic?

There are coordinates marked on the edge of the schematic.

[The Dude]

Parts are at F2 Page 2, Jazz.

Joe, It looks like you may have had a catastrophic output tube failure. Can you remove the output tubes, fire it up and post the voltages on the output tube sockets? I'm assuming J22 and J23 go to another board for the output tubes (not shown)?

P.S. Those things are notorious for having ribbon cable problems. Check continuity on every pin of the cable connections to the output tube board.

[GrumpyJoe]

yes I will post the voltages as soon as I get home.

[Enzo]

The output tube board is the right side image in post #1

Those two multipin connectors are right on the power tube board and main board. the tube board plugs onto the main board. No ribbons, just those inline connectors direct. the pin connections can still fail of course.

[The Dude]

Oh silly me. I didn't realize it was 2 separate images. Thanks for pointing out my idiocy!

Edit: As far as the ribbon cables, I must be thinking of a different model Blue Voodoo. I've bypassed ribbon cables in several.

[Enzo]

Always happy to make folks feel stupid.

No need to repay the favor...

[GrumpyJoe]

Ok fellas. Sorry it took me so long. We've been blasted by snow and the net has been out. Here are the voltages with the power tubes removed.

J22 tube:
Pin 1: -2.05vdc
Pin 2: 0
Pin 3: 542vdc
Pin 4: 533vdc
Pin 5: -31.83vdc
Pin 6: -31.75 vdc
Pin 7: 0
Pin 8: -2.05vdc

J23 tube:
Pin 1: -2.42vdc
Pin 2: 0
Pin 3: 0.42svc
Pin 4: 530vdc
Pin 5: -31.5vdc
Pin 6: 0
Pin 7: 0
Pin 8: -2.42vdc

[The Dude]

You are missing the plate voltage on the J23 tube (pin 3). You need to track down where it is getting lost. It comes out of the OT to the plate of the tube through the connectors.

[Enzo]

I assume you are reading voltages at the tube socket, not J22 and J23 themselves.

Do the power tubes heat up? You show zero volts, but I will assume that is on DC. Is there 6vAC between pins 2 and 7? or 3vAC from pins 2 and 7 to ground?

Also note the second tube has lost its B+ on the plate, pin 3.

Also that negative 2v on the cathodes is suspect. Where is your meter grounded. Are the two cathode fuses OK on the main board? Or power down, is there roughly 12 ohms to ground from pin 8 of each socket?

[GrumpyJoe]

Yes I am measuring the voltages at the sockets. I will measure your last suggestions and post them in a few. I appreciate your help fellas.

[GrumpyJoe]

I am grounding my meter on the chassis with a screw on alligator clip. The two fuses both test good. Here's my latest readings. I am using J22 and J23 only as a reference to the individual tubes.

J22:
Pin 2 to pin 7: 6.9vac
Pin 2 to ground: 1.32vac
Pin 7 to ground: 582Mvac
Pin 8 to ground: 411k ohms

J23:
Pin 2 to pin 7: 6.85vac
Pin 2 to ground: 585Mvac
Pin 7 to ground: 1.28vac
Pin 8 to ground: 1 megaohm

[Enzo]

Pin 8, you cannot measure resistance while the amp is powered, were we trying to do that? If that 400k and 1meg resistance readings from cathodes to ground is true, then your cathode path is open. Power off, measure resistance from pin 8 direct to the fuse for that tube, do both. Are they all continuous? Or is the connection open (or 400k and 1 meg?) And do you get 12 ohms from each fuse to ground?

[GrumpyJoe]

Duh. One of my brainfarts. Lol. I'll recheck it now

[GrumpyJoe]

Ok. With the amp OFF, lol, I get "over limit" reading from pin 8 to ground on both tubes and from pin 8 to the far side of the fuses I get 10.8 ohms on both.